Process for preparing cellular glass slabs



July 13, 1948. A. H. BAKER 2,445,298

PROCESS FOR PREPARING CELLULAR amass SLABS 5 Sheets-Sheet 1 Original Filed March 31, 1945 F f F July 13, 1948. A, H, BAKER 2,445,298

PROCESS FOR PREPARING CELLULAR GLASS SLA BS Original Filed March 51, 1945 3 Sheets-sheet 2 1 F o 7 I l- 28 I 2x 44 l l v l I l l l I i l I I INVENTOR. fl-H 54kt? Sag/8% HTTOAA/EK July 13, 1948.

A. H. BAKER PROCESS FOR PREPARING CELLULAR GLASS SLABS Original Filed March 51, 1945 3 Sheets-Sheet 3 INVENTOR. AMER 6? j BY 1 I HTTOE/WFK Patented July 13, 1948 PROCESS FOR PREPARING CELLULAR GLASS SLABS Arvid H. Baker,

Pittsburgh Port Allegany, Pa., Corning Corporation,

County, Pa., a corporation of Pennsylvania assignor to Alleghenl Original application March 31, 1945, Serial No.

1 Claim.

The present invention relates to a process of preparing cellular glass slabs or blocks from a mixture of pulverized glass and a gassing agent.

The invention described and claimed herein constitutes a division of my copending application, Ser. No. 585,833, filed March 31, 1945, for Molds and use of the same in the'cellulation of glass.

.One object of the invention is to provide a simple and economical method of shaping and annealing slabs of cellulated glass.

These and other objects will be apparent from consideration of the following specification and the appended claim.

For a better understanding of the invention reference now may be had to the accompanying drawings in which like numerals refer to like parts and in which:

Figure 1 is a sectional view of a mold for forming cellular glass and being constructed in accordance with the provisions of the present invention.

Figure 2 is a plan view of a mold section embodying the principles ofthe invention.

Figure 3 is a sectional view taken substantially upon the line III-III of Figure 2.

Figure 4 is a fragmentary diagrammatic view of a furnace and an annealing lehr for use in the practice of the invention.

Figure 5 is an elevational view of a cellular slab as obtained from the mold constructed in accordance with the invention.

Figure 6 is a fragmentary view illustrating the treatment of a cellular slab prior to subjecting it to the annealing operation.

Figure 7 is an elevational view illustrating an annealing lehr used in the practice of the invention.

Figure 8 is a sectional view of a modified form of mold.

It has heretofore been proposed to prepare an insulating material of low density suitable for use in the thermal insulation of various structures and also for use as a buoyant element in life rafts and various types of floats by heating mixtures of finely pulverized glass and a pulverulent gassing agent such as finely powdered carbon to the temperature of softening of the glass, e. g. to a temperature approximately of 1600 or 1650 F. or course, a mold of suitable contour and of a material of high resistance to heat and hot gases is required. The resultant bodies (usually slabs or blocks) are subsequently removed from the molds and subjected to a slow and careful annealing ope at o in or e to relieve internal stresses in the Divided and this application August Serial No. 692,210 I cellulated glass. One of the great difficulties heretofore encountered in the. preparation of cellular glass by this method has consisted in the extreme difficulty in obtaining molds which were inexpensive and which would withstand the severe conditions of operation over a sufficient period of time to render them feasible for commercial use.

In accordance with the provisions of the present invention, applicant provides a mold structure which includes top and bottom sections which may be of the same or of different depth and which are bread pan-like or frust'o-pyramidal in shape. The two sections are so formed that one can be superposed in inverted position upon the other to provide a closed chamber suitable for containing the mixture of powdered glass and gassing agent during the cellulating operation. As a further feature, the invention contemplates a formation of cellular slabs or blocks having wide faces and narrow edges to such a contour'as to admit of setting them on edge in the annealin lehr in such a position as to facilitate uniform annealing with a minimum wastage of'space and apparatus.

Molds'A- or A suitable for forming cellular blocks in accordance with the provisions of the invention are shown in section in Figures 1 and 2 of the drawings are formed of stainless sheet steel of heavy gauge and include top and bottom portions 1 l-I2 and l |--|2' which may be identical in size and shape as shown in Figure 1 or as shown in Figure 8, the top section being somewhat deeper than the bottom section. The sections include plain bottom walls |3-l4 and l3'- l4. Of course, when the sections ll--l I are inverted upon the sections |2-l 2' the walls 13-43 become the tops of the mold chambers. Each section'is also provided with side walls, l6, l1, l8, and I9; or IE, l1, l8, and I9. It is to be observed that the walls 16-11-49 and l6-l'l- 19' are substantially beveled in order to assure a high degree of clearance, thus facilitating the re moval ofthe cellular glass blocks from the molds after they have been formed. The walls l8 or 18' are but slightly beveled, thus providing each block with an edge portion which is nearly flat for a purpose which will be apparent later.

Small holes, e. g., /32 inch in diameter indicated at 20 at each corner and in the middle of the sections prevent imprisonment of air in the molds as the mass bloats up. The molds are provided with edge flanges 2 l-2 l extending entirely about the perimeter and preferably being flattened in such a manner as to provide a smooth 3 surface of contact between the top and bottom and the bottom sections. The top mold section sections when they are arranged in superposed can then be tipped up about the flange of the position. The edges are also formed with down wall it? or id as a fulcrum as indicated in dot turned lip portions 2222 which serve to and dash line position X in Figure 1. The top strengthen the flange and assure that the por- 5 section can then easily be lifted" oil and the tions 2|2l will remain smooth and fiat even bottom section removed from the slab. The slopafter repeated heatings and coolings. ing sides to provide clearance to permit the In the practice of the invention, the molds are: tipping motion.

thinly coated internally with a, slurry of clay,. T cellular slab r block 2 at h stage i bauxite, or the like and the coating dried. The=10 of approximately the outline shown in Figure 5 bottom portion of the mold is partially filled, and comprises substantially'wedge or V-like pore. g. to the line Y with a pulverulent mixture of tions 29 about three edges and a base at which very finely powdered glass and carbon. In this is more nearly a operation, glass powdered to a'fineness such that The Slabs at this me are sufficiently Co ed most of it Will pass through-a screen of 200 or p n their a s o permit them to be han black which is used in a ratio of about 0.5%, alqu ot, probably almost as hot as the mathough somewhat more or somewhat less may terl'alwithin e l a 'n f nac be sometimes employed. A promoter of cellular p p es of annealing the slab, the base tion such as antimony trioxide or calcium-sulfate portion Shown in Figure 5 i u d upon an is alsoadded in a small amount, e. g. 0.3%. abrasive elementsuch as a'sheet 32 of h i These ingredients'are thoroughlyrintermixed; and fabric or h r a rasion resistant foraminous leveled Ofi'fill the bottom section, andthe top matelialshown in Figures 4 a d 6 adapted to section-is superposed. The molds are then subeXeTten ableiding action The Slabs y reason jected to a-heating operation in 3,,guitab1e-f11rof oellulatedstructure, are quite readily abraded nace such as aroller hearth, furnace 23 illusby'fl'ictl'oniagainst t e ab ding member and are trated diagrammatically i Figure 4, Th fur easily flattened to form a base vertical to the nace comprises an elongated'shell Moi refraoaces ofthe slabs which permits the blocks or tory material which is supported upon vertical Slabs testand up Vertically W en hey are dismembers 26; The moldsare carried through posed afiat surface. the furnaceinareclining positionupo'n a-seriesof Aftelthe Slabs h be n removed from the continuously drivenrollers 25, several of which molds, and the base Dortiens flattened, y e are disposed externally of the mouth of the fur Set 9 as Shown in Figure 7 n V rtical posltlon c t provide a loading platform 25' and and ill-spaced relation upon a chain conveyor other series at the exit end of the. furnace probelt running n in sly at slow speed viding an unloading platform 21, through an annealing lehr M where the temper- The molds as they progress throughout the-fur ature is brought dOWll gradually and as evenly nace upon the'rollers,are-graduallyheated to the as Possible thmllgh e t al ran e. 'Lehr 34, temperature of:sintering;of the glass in the'miX- 40 t d counterweighted Vertically S dture. This temperature; should never be sufii lngdoor 36 o keep out Cold air. i m; t t-th glass clownv intoa truly fluid The forms of the invention herein illustrated state, but should only be' sufiiciently high to are to be c0nsidered as being y Way of examrender it; tacky and somewhat plastic-and to ple. It will be apparent to'those skilled in=the generate the gases. .This,.-temperature'for most that numerous modifications may b made g asse such a sa conventional one predomj therein Without'departure from the Spirit Of the nanfly, Mme, soda and silica, employed in with invention orthe scope of the appended claim. dows, bottles, "and the like, is approximately: What I claim 1600 or- 1650 F. The molds: neartheend of n h p s f forming c llular las slabs theheatingoperation are completely filledwith so having relatively W faces and narr w d es, a mass of'coherent glass bloated or'cellulated by by sintering p v ed glass adm xed With a minute bubblesof gaseseenerated by the reacgassmg agent in bread pan-like molds each-com tion of the-gassing agent :at th'e'temperature of p ns a i n of f py mid l hap and cellulation. having'sloping sides and a flat bottom whereby I order to remove the mold fr m; the cellu- 55 to impart to slabs formed therein beveled edges lar bodies, it is preferred firstto cool-the molds designed to admit of ready release of the slabs downsomewhat, for example, to 800 or 900 from the molds; the stepsof removing the freshly and'then to'sub'ject them to sudden shockheat formed slabs from the molds rubbing one of-the ing which expands the molds without substand es of each p n a lasl m be o p tia l expanding the" poorly conductive glass'mavi e a fiat a t ri ht an e to h f es of ciently expanded to permit the sections to 'be' sition by circulationof air about and between pried-apart quite readily by-theinsertion of a 5 them; blunt instrument between theflanges of-s'thec-top ARVID H. BAKER; 

